Q: Apple Mail with Yosemite

I have tried the connection doctor, and says that everything is fine. All circles in green, servers connected and no errors. That´s why i´m confused and it´s awkward that it sends the email to the outbox. I don´t know if it´s because of Yosemite or maybe because the Mailbox is to big and it´s creating problems, but in other Mac´s we don´t have that problem.

Thanks for answering so fast.